Nonwoven fabrics are generally prepared by randomly assembling individual fibers to form a web and bonding the fibers by chemical, thermal, or mechanical means. Generally, the fibers are bonded by impregnating the web with a binder for the nonwoven material and heating the web at an effective temperature to volatilize the carrier and induce fiber/binder adhesion. These nonwoven fibrous materials are known to possess distinct advantages over conventional woven materials. Some of these advantages include absence of raveling, smoother surfaces, increased softness, improved hand, greater absorbency, improved loft, etc.
The binders used to impregnate nonwoven webs are typically aqueous polymeric dispersions or aqueous polymeric latices which form tough, coherent films upon drying. A wide variety of polymers are known to be used as latex binders. Latices including polymers made from the following monomers or monomer blends of vinyl acetate, styrene/butadiene, vinyl acetate/acrylate monomers, vinyl acetate/ethylene, acrylic acid esters, and the like are generally known. Any of the above polymers can be copolymerized with many different vinyl monomers having functional groups such as amide, methylol, glycidyl, carboxyl, isocyanate, etc.
Caimi et al., U.S. Pat. No. 4,176,108 discloses a latex binder for nonwoven webs comprising an acrylate and/or vinyl acetate based copolymer containing 2-hydroxyethyl or 2-hydroxypropyl acrylate or methacrylate, which is combined with an anionic and nonionic surfactant.
Acrylic based polymers and copolymers used in adhesive formulations are well known. Wolinski et al., U.S. Pat. No. 4,230,613 discloses a lacquer composition for coating a substrate, comprising acrylic polymers such as methyl methacrylate/butyl acrylate/acrylic acid terpolymers, a volatile solvent such as a mixture of toluene and isopropanol, and a tertiary amine activator.
When nonwoven fabric materials are made from water swellable, soluble or sensitive fibers, there are inherent problems, i.e., shrinkage and dissolution of the fibers, associated with the saturation, spray or print bonding of an aqueous-based binder onto such fibers, preventing the formation of a structurally sound nonwoven web. Therefore, a non-aqueous adhesive binder is needed for use in making nonwoven water swellable, soluble or sensitive fiber-based materials, so that the adhesive effectively binds such fibers to form a structurally sound nonwoven web.